Pulling-up-type continuous casting method and pulling-up-type continuous casting apparatus

ABSTRACT

A pulling-up-type continuous casting method according to an aspect of the present invention includes disposing a shape defining member ( 102 ) above a molten-metal surface of molten metal (M 1 ) held in a holding furnace ( 101 ), the shape defining member ( 102 ) being configured to define a cross-sectional shape of a cast-metal article (M 3 ) to be cast, submerging a starter (ST) into the molten metal (M 1 ) while making the starter (ST) pass through the shape defining member ( 102 ), and pulling up the molten metal (M 1 ) by pulling up the starter (ST) while making the molten metal (M 1 ) pass through the shape defining member ( 102 ) after a temperature of the shape defining member ( 102 ) reaches a predetermined reference temperature. The reference temperature is equal to or higher than a solidification completion temperature of the molten metal (M 1 ).

TECHNICAL FIELD

The present invention relates to a pulling-up-type continuous casting method and a pulling-up-type continuous casting apparatus.

BACKGROUND ART

Patent Literature 1 proposes a free casting method as a revolutionary pulling-up-type continuous casting method that does not requires any mold. As shown in Patent Literature 1, after a starter is submerged under the surface of a melted metal (molten metal) (i.e., molten-metal surface), the starter is pulled up, so that some of the molten metal follows the starter and is drawn up by the starter by the surface film of the molten metal and/or the surface tension. Note that it is possible to continuously cast a cast-metal article having a desired cross-sectional shape by drawing the molten metal and cooling the drawn molten metal through a shape defining member disposed in the vicinity of the molten-metal surface.

In the ordinary continuous casting method, the shape in the longitudinal direction as well as the shape in cross section is defined by the mold. In the continuous casting method, in particular, since the solidified metal (i.e., cast-metal article) needs to pass through the inside of the mold, the cast-metal article has such a shape that it extends in a straight-line shape in the longitudinal direction.

In contrast to this, the shape defining member used in the free casting method defines only the cross-sectional shape of the cast-metal article, while it does not define the shape in the longitudinal direction. As a result, cast-metal articles having various shapes in the longitudinal direction can be produced by pulling up the starter while moving the starter (or the shape defining member) in a horizontal direction. For example, Patent Literature 1 discloses a hollow cast-metal article (i.e., a pipe) having a zigzag shape or a helical shape in the longitudinal direction rather than the straight-line shape.

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No. 2012-61518

SUMMARY OF INVENTION Technical Problem

The present inventors have found the following problem.

In the free casting method disclosed in Patent Literature 1, when the shape defining member is not sufficiently heated, in particular, at the start of casting and the like, the molten metal that follows the bottom end of the starter being pulled up solidifies as the molten metal comes into contact with the shape defining member when the starter passes through the shape defining member in some cases. In such cases, the solidified pieces get snagged on the shape defining member, causing surface defects such as peeling and curling in the cast-metal article near the boundary between the starter and the cast-metal article.

The present invention has been made in view of the above-described problem, and an object thereof is to provide a pulling-up-type continuous casting method and a pulling-up-type continuous casting apparatus in which the surface defects in the cast-metal article near the boundary between the starter and the cast-metal article is prevented.

Solution to Problem

A pulling-up-type continuous casting method according to an aspect of the present invention includes:

-   -   disposing a shape defining member above a molten-metal surface         of molten metal held in a holding furnace, the shape defining         member being configured to define a cross-sectional shape of a         cast-metal article to be cast;     -   submerging a starter into the molten metal while making the         starter pass through the shape defining member; and     -   pulling up the molten metal by pulling up the starter while         making the molten metal pass through the shape defining member         after a temperature of the shape defining member reaches a         predetermined reference temperature, in which     -   the reference temperature is equal to or higher than a         solidification completion temperature of the molten metal.

In the pulling-up-type continuous casting method according to this aspect of the present invention, the molten metal is pulled up by pulling up the starter while making the molten metal pass through the shape defining member after the temperature of the shape defining member reaches the predetermined reference temperature. Note that the reference temperature is equal to or higher than the solidification completion temperature of the molten metal. Therefore, the solidification of the molten metal, which would otherwise occur due to the contact between the molten metal following the bottom end of the starter being pulled up and the shape defining member, can be prevented, thus preventing the surface defects in the cast-metal article near the boundary between the starter and the cast-metal article.

A pulling-up-type continuous casting apparatus according to an aspect of the present invention includes:

-   -   a holding furnace that holds molten metal;     -   a shape defining member disposed above a molten-metal surface of         the molten metal, the shape defining member being configured to         define a cross-sectional shape of a cast-metal article to be         cast;     -   a temperature sensor that measures a temperature of the shape         defining member;     -   a pulling-up machine that pulls up the molten metal by pulling         up a starter while making the molten metal pass through the         shape defining member; and     -   a casting control unit that starts the pulling-up by the         pulling-up machine after the temperature of the shape defining         member measured by the temperature sensor reaches a         predetermined reference temperature, in which     -   the reference temperature is equal to or higher than a         solidification completion temperature of the molten metal.

The pulling-up-type continuous casting apparatus according to this aspect of the present invention includes the casting control unit that starts the pulling-up by the pulling-up machine after the temperature of the shape defining member measured by the temperature sensor reaches the predetermined reference temperature. Note that the reference temperature is equal to or higher than the solidification completion temperature of the molten metal. Therefore, the solidification of the molten metal, which would otherwise occur due to the contact between the molten metal following the bottom end of the starter being pulled up and the shape defining member, can be prevented, thus preventing the surface defects in the cast-metal article near the boundary between the starter and the cast-metal article.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a pulling-up-type continuous casting method and a pulling-up-type continuous casting apparatus in which the surface defects in the cast-metal article near the boundary between the starter and the cast-metal article is prevented.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross section of a free casting apparatus according to a first exemplary embodiment;

FIG. 2 is a plane view of a shape defining member 102 according to the first exemplary embodiment;

FIG. 3 is a block diagram of a casting control system provided in a free casting apparatus according to the first exemplary embodiment;

FIG. 4 is an enlarged cross section schematically showing a state where a starter ST passes through a shape defining member 102 after the temperature of the shape defining member 102 reaches a reference temperature;

FIG. 5 is an enlarged cross section schematically showing a state where the starter ST passes through the shape defining member 102 before the temperature of the shape defining member 102 reaches the reference temperature;

FIG. 6 is a macro-photograph showing a state where a starter ST is pulled up through a shape defining member 102 when the temperature of the shape defining member 102 is 650 degrees C., which is higher than a reference temperature;

FIG. 7 is a macro-photograph showing a state where the starter ST is pulled up through the shape defining member 102 when the temperature of the shape defining member 102 is 200 degrees C., which is lower than the reference temperature;

FIG. 8 is a plane view of a shape defining member 102 according to a modified example of the first exemplary embodiment;

FIG. 9 is a side view of a shape defining member 102 according to a modified example of the first exemplary embodiment;

FIG. 10 is an enlarged cross section schematically showing a shape defining member 202 of a free casting apparatus according to a second exemplary embodiment; and

FIG. 11 is a block diagram of a casting control system provided in a free casting apparatus according to the second exemplary embodiment.

DESCRIPTION OF EMBODIMENTS

Specific exemplary embodiments to which the present invention is applied are explained hereinafter in detail with reference to the drawings. However, the present invention is not limited to exemplary embodiments shown below. Further, the following descriptions and the drawings are simplified as appropriate for clarifying the explanation.

First Exemplary Embodiment

Firstly, a free casting apparatus (pulling-up-type continuous casting apparatus) according to a first exemplary embodiment is explained with reference to FIG. 1. FIG. 1 is a schematic cross section of a free casting apparatus according to the first exemplary embodiment. As shown in FIG. 1, the free casting apparatus according to the first exemplary embodiment includes a molten-metal holding furnace 101, a shape defining member 102, a support rod 104, an actuator 105, a cooling gas nozzle 106, a cooling gas supply unit 107, a pulling-up machine 108, and a temperature sensor 110.

Note that needless to say, the right-hand xyz-coordinate system shown in FIG. 1 is illustrated for the sake of convenience, in particular, for explaining the positional relation among components. In FIG. 1, the xy-plane forms a horizontal plane and the z-axis direction is the vertical direction. More specifically, the positive direction on the z-axis is the vertically upward direction.

The molten-metal holding furnace 101 contains molten metal M1 such as aluminum or its alloy, and maintains the molten metal M1 at a predetermined temperature (e.g., about 720 degrees C.) at which the molten metal M1 has fluidity. In the example shown in FIG. 1, since the molten-metal holding furnace 101 is not replenished with molten metal during the casting process, the surface of molten metal M1 (i.e., molten-metal surface) is lowered as the casting process advances. Alternatively, the molten-metal holding furnace 101 may be replenished with molten metal as required during the casting process so that the molten-metal surface is kept at a fixed level. Note that the position of the solidification interface SIF can be raised by increasing the setting temperature of the molten-metal holding furnace 101 and the solidification interface SIF can be lowered by lowering the setting temperature of the molten-metal holding furnace 101. Needless to say, the molten metal M1 may be a metal other than aluminum and an alloy thereof.

The shape defining member 102 is made of ceramic or stainless, for example, and disposed above the molten metal M1. The shape defining member 102 defines the cross-sectional shape of cast metal M3 to be cast. The cast metal M3 shown in FIG. 1 is a plate or a solid cast-metal article having a rectangular shape in a horizontal cross section (hereinafter referred to as “lateral cross section”). Note that needless to say, there are no particular restrictions on the cross-sectional shape of the cast metal M3. The cast metal M3 may be a hollow cast-metal article such as a circular pipe and a rectangular pipe.

In the example shown in FIG. 1, the shape defining member 102 is disposed so that its bottom-side main surface (bottom surface) is in contact with the molten-metal surface. Therefore, it is possible to prevent oxide films formed on the surface of the molten metal M1 and foreign substances floating on the surface of the molten metal M1 from entering the cast metal M3. Further, the shape defining member 102 can be easily heated by the molten metal M1.

Alternatively, the shape defining member 102 may be disposed so that its bottom surface is a predetermined distance (e.g., about 0.5 mm) away from the molten-metal surface. When the shape defining member 102 is disposed a certain distance away from the molten-metal surface, the thermal deformation and the erosion of the shape defining member 102 is prevented, thus improving the durability of the shape defining member 102.

FIG. 2 is a plane view of the shape defining member 102 according to the first exemplary embodiment. Note that the cross section of the shape defining member 102 shown in FIG. 1 corresponds to a cross section taken along the line I-I in FIG. 2. As shown in FIG. 2, the shape defining member 102 has, for example, a rectangular shape as viewed from the top, and has a rectangular opening (molten-metal passage section 103) having a thickness t1 and a width w1 at the center thereof

Note that the temperature sensor 110, which is fixed on the top-side main surface (top surface) of the shape defining member 102, is also shown in FIG. 2. Further, the xyz-coordinate system shown in FIG. 2 corresponds to that shown in FIG. 1.

As shown in FIG. 1, the molten metal M1 follows the cast metal M3 and is pulled up by the cast metal M3 by its surface film and/or the surface tension. Further, the molten metal M1 passes through the molten-metal passage section 103 of the shape defining member 102. That is, as the molten metal M1 passes through the molten-metal passage section 103 of the shape defining member 102, an external force(s) is applied from the shape defining member 102 to the molten metal M1 and the cross-sectional shape of the cast metal M3 is thereby defined. Note that the molten metal that follows the cast metal M3 and is pulled up from the molten-metal surface by the surface film of the molten metal and/or the surface tension is called “held molten metal M2”. Further, the boundary between the cast metal M3 and the held molten metal M2 is the solidification interface SIF.

The support rod 104 supports the shape defining member 102.

The support rod 104 is connected to the actuator 105. By the actuator 105, the shape defining member 102 can be moved in the up/down direction (vertical direction, i.e., z-axis direction) through the support rod 104. With this configuration, it is possible to move the shape defining member 102 downward as the molten-metal surface is lowered due to the advance of the casting process.

The cooling gas nozzle (cooling section) 106 is cooling means for spraying a cooling gas (for example, air, nitrogen, or argon) supplied from the cooling gas supply unit 107 on the cast metal M3 and thereby cooling the cast metal M3. The position of the solidification interface SIF can be lowered by increasing the flow rate of the cooling gas and the position of the solidification interface SIF can be raised by reducing the flow rate of the cooling gas. Note that the cooling gas nozzle 106 can also be moved in the up/down direction (vertical direction, i.e., z-axis direction) and the horizontal direction (x-axis direction and/or y-axis direction). Therefore, for example, it is possible to move the cooling gas nozzle 106 downward in conformity with the movement of the shape defining member 102 as the molten-metal surface is lowered due to the advance of the casting process. Alternatively, the cooling gas nozzle 106 can be moved in a horizontal direction in conformity with the horizontal movement of the pulling-up machine 108.

By cooling the cast metal M3 by the cooling gas while pulling up the cast metal M3 by using the pulling-up machine 108 connected to the starter ST, the held molten metal M2 located in the vicinity of the solidification interface SIF is successively solidified from its upper side (the positive side in the z-axis direction) toward its lower side (the negative side in the z-axis direction) and the cast metal M3 is formed. The position of the solidification interface SIF can be raised by increasing the pulling-up speed of the pulling-up machine 108 and the position of the solidification interface SIF can be lowered by reducing the pulling-up speed. Further, the shape in the longitudinal direction of the cast metal M3 can be arbitrarily changed by pulling up the cast metal M3 while moving the pulling-up machine 108 in a horizontal direction (x-axis direction and/or y-axis direction). Note that the shape in the longitudinal direction of the cast metal M3 may be arbitrarily changed by moving the shape defining member 102 in a horizontal direction instead of moving the pulling-up machine 108 in a horizontal direction.

Note that in order to obtain a cast-metal article M3 having an accurate size and excellent surface quality, the solidification interface SIF is kept at an appropriate position (height). That is, the casting is performed in a state where the solidifying speed in the solidification interface SIF is substantially balanced by the pulling-up speed. In view of productivity, it is desirable that the pulling-up speed be greater. However, if the pulling-up speed is increased while the solidifying speed is unchanged, the solidification interface SIF rises, thus causing the held molten metal M2 to be torn off. As described above, the solidifying speed can be increased (i.e., the solidification interface SIF can be lowered) by increasing the flow rate of the cooling gas and/or lowering the molten metal temperature.

The temperature sensor 110 measures the temperature of the shape defining member 102. In the example shown in FIG. 1, the temperature sensor 110 is a thermocouple. As shown in FIG. 1, the temperature sensor 110 is preferably fixed in the vicinity of the molten-metal passage section 103 on the top surface of the shape defining member 102. Note that the temperature sensor 110 is not limited to the thermocouple. That is, other contact-type temperature sensors may be used. Further, non-contact-type temperature sensors may also be used. The contact-type temperature sensor enables more accurate temperature measurement.

The free casting apparatus according to the first exemplary embodiment can measure the temperature of the shape defining member 102 by the temperature sensor 110. Therefore, at the start of casting, it is possible to start pulling up the starter ST after the temperature of the shape defining member 102 reaches the solidification completion temperature (solidus temperature) of the molten metal M1 or a higher temperature. As a result, the solidification of the held molten metal M2, which would otherwise occur due to the contact between the held molten metal M2 following the starter ST being pulled up and the shape defining member 102, can be prevented, thus preventing the occurrence of the surface defects in the cast metal M3 near the boundary between the starter ST and the cast metal M3. Note that it is further preferable that the pulling-up of the starter ST through the shape defining member 102 be started after the temperature of the shape defining member 102 reaches the solidification start temperature (liquidus temperature) of the molten metal M1. Note that in the case of pure metal, both the solidification completion temperature and the solidification start temperature correspond to the melting point of that metal and thus are equal to each other.

Next, a casting control system provided in a free casting apparatus according to the first exemplary embodiment is explained with reference to FIG. 3. FIG. 3 is a block diagram of a casting control system provided in a free casting apparatus according to the first exemplary embodiment. As shown in FIG. 3, this casting control system includes a shape defining member 102, a pulling-up machine 108, a temperature sensor 110, and a casting control unit 111. Note that the shape defining member 102, the pulling-up machine 108, and the temperature sensor 110 have already been explained with reference to FIG. 1, and therefore their detailed explanation is omitted here.

The casting control unit 111 includes a storage unit (not shown) that memorizes the reference temperature of the shape defining member 102 which is used when the starter ST starts to be pulled up from the molten metal M1. Then, when the temperature of the shape defining member 102 measured by the temperature sensor 110 is lower than the reference temperature, the casting control unit 111 does not start the pulling-up of the starter ST by the pulling-up machine 108. On the other hand, when the temperature of the shape defining member 102 measured by the temperature sensor 110 reaches the reference temperature, the casting control unit 111 starts the pulling-up of the starter ST by the pulling-up machine 108.

Note that the reference temperature is equal to or higher than the solidification completion temperature of the molten metal M1. When the reference temperature is lower than the solidification completion temperature of the molten metal M1, the held molten metal M2 that follows the bottom end of the starter ST being pulled up solidifies as the held molten metal M2 comes into contact with the shape defining member 102. As a result, surface defects such as peeling and curling tend to occur in the cast metal M3. On the other hand, when the reference temperature is equal to or higher than the solidification completion temperature of the molten metal M1, the held molten metal M2 hardly solidifies even when the held molten metal M2 comes into contact with the shape defining member 102. Further, when the reference temperature is equal to or higher than the solidification start temperature, theoretically the held molten metal M2 does not solidify even when the held molten metal M2 comes into contact with the shape defining member 102. Therefore, the reference temperature is preferably equal to or higher than the solidification start temperature.

FIG. 4 is an enlarged cross section schematically showing a state where the starter ST passes through the shape defining member 102 after the temperature of the shape defining member 102 reaches the reference temperature. That is, FIG. 4 shows an example according to the first exemplary embodiment. As shown in FIG. 4, when the temperature of the shape defining member 102 is higher than the reference temperature, the solidification of the held molten metal M2, which would otherwise occur due to the contact between the held molten metal M2 following the starter ST being pulled up and the shape defining member 102, is prevented.

In contrast to this, FIG. 5 is an enlarged cross section schematically showing a state where the starter ST passes through the shape defining member 102 before the temperature of the shape defining member 102 reaches the reference temperature. That is, FIG. 5 shows a comparative example of the first exemplary embodiment. As shown in FIG. 5, when the temperature of the shape defining member 102 is lower than the reference temperature, a solidified piece(s) M21 is generated in the boundary between the starter ST and the shape defining member 102 as the held molten metal M2 following the starter ST being pulled up comes into contact with the low-temperature shape defining member 102.

Note that the xyz-coordinate systems shown in FIGS. 4 and 5 correspond to that shown in FIG. 1.

FIG. 6 is a macro-photograph showing a state where the starter ST is pulled up through the shape defining member 102 when the temperature of the shape defining member 102 is 650 degrees C., which is higher than the reference temperature. That is, FIG. 6 shows an example according to the first exemplary embodiment. As shown in FIG. 6, when the temperature of the shape defining member 102 is higher than the reference temperature, the surface defects in the cast metal M3, which would otherwise occur near the boundary between the starter ST and the cast metal M3, is prevented.

In contrast to this, FIG. 7 is a macro-photograph showing a state where the starter ST is pulled up through the shape defining member 102 when the temperature of the shape defining member 102 is 200 degrees C., which is lower than the reference temperature. That is, FIG. 7 shows a comparative example of the first exemplary embodiment. As shown in FIG. 7, when the temperature of the shape defining member 102 is lower than the reference temperature, surface defects M22 such as peeling and curling in the cast metal M3 occur near the boundary between the starter ST and the cast metal M3.

Next, a free casting method according to the first exemplary embodiment is explained with reference to FIG. 1.

Firstly, the starter ST is lowered by the pulling-up machine 108 and made to pass through the molten-metal passage section 103 of the shape defining member 102, and the tip (bottom) of the starter ST is submerged into the molten metal M1.

Next, the starter ST starts to be pulled up at a predetermined speed. Note that even when the starter ST is pulled away from the molten-metal surface, the molten metal M1 follows the starter ST and is pulled up from the molten-metal surface by the surface film and/or the surface tension. That is, the held molten metal M2 is formed. As shown in FIG. 1, the held molten metal M2 is formed in the molten-metal passage section 103 of the shape defining member 102. That is, the held molten metal M2 is shaped into a given shape by the shape defining member 102.

As described above, in the free casting method according to the first exemplary embodiment, the starter ST starts to be pulled up after the temperature of the shape defining member 102 reaches the solidification completion temperature of the molten metal M1 or a higher temperature. As a result, the solidification of the held molten metal M2, which would otherwise occur due to the contact between the held molten metal M2 following the starter ST being pulled up and the shape defining member 102, can be prevented, thus preventing the occurrence of the surface defects in the cast metal M3 near the boundary between the starter ST and the cast metal M3.

Next, since the starter ST or the cast metal M3 is cooled by a cooling gas, the held molten metal M2 is indirectly cooled and successively solidifies from its upper side toward its lower side. As a result, the cast metal M3 grows. In this manner, it is possible to continuously cast the cast metal M3.

Modified Example of First Exemplary Embodiment

Next, a free casting apparatus according to a modified example of the first exemplary embodiment is explained with reference to FIGS. 8 and 9. FIG. 8 is a plane view of a shape defining member 102 according to a modified example of the first exemplary embodiment. FIG. 9 is a side view of the shape defining member 102 according to the modified example of the first exemplary embodiment. Note that the xyz-coordinate systems shown in FIGS. 8 and 9 also correspond to that shown in FIG. 1.

The shape defining member 102 according to the first exemplary embodiment shown in FIG. 2 is composed of one plate. Therefore, the thickness t1 and the width w1 of the molten-metal passage section 103 are fixed. In contrast to this, the shape defining member 102 according to the modified example of the first exemplary embodiment includes four rectangular shape defining plates 102 a, 102 b, 102 c and 102 d as shown in FIG. 8. That is, the shape defining member 102 according to the modified example of the first exemplary embodiment is divided into a plurality of sections. With this configuration, it is possible to change the thickness t1 and the width w1 of the molten-metal passage section 103. Further, the four rectangular shape defining plates 102 a, 102 b, 102 c and 102 d can be moved in unison in the z-axis direction.

As shown in FIG. 8, the shape defining plates 102 a and 102 b are arranged to be opposed to each other in the y-axis direction. Further, as shown in FIG. 9, the shape defining plates 102 a and 102 b are disposed at the same height in the z-axis direction. The gap between the shape defining plates 102 a and 102 b defines the width w1 of the molten-metal passage section 103. Further, since each of the shape defining plates 102 a and 102 b can be independently moved in the y-axis direction, the width w1 can be changed.

Note that the temperature sensor 110 is fixed in the vicinity of the molten-metal passage section 103 on the top surface of the shape defining plate 102 b.

Further, as shown in FIGS. 8 and 9, a laser displacement gauge S1 and a laser reflector plate S2 may be provided on the shape defining plates 102 a and 102 b, respectively, in order to measure the width w1 of the molten-metal passage section 103.

[0038] Further, as shown in FIG. 8, the shape defining plates 102 c and 102 d are arranged to be opposed to each other in the x-axis direction. Further, the shape defining plates 102 c and 102 d are disposed at the same height in the z-axis direction. The gap between the shape defining plates 102 c and 102 d defines the thickness t1 of the molten-metal passage section 103. Further, since each of the shape defining plates 102 c and 102 d can be independently moved in the x-axis direction, the thickness t1 can be changed.

The shape defining plates 102 a and 102 b are disposed in such a manner that they are in contact with the top sides of the shape defining plates 102 c and 102 d.

Next, a driving mechanism for the shape defining plate 102 a is explained with reference to FIGS. 8 and 9. As shown in FIGS. 8 and 9, the driving mechanism for the shape defining plate 102 a includes slide tables T1 and T2, linear guides G11, G12, G21 and G22, actuators A1 and A2, and rods R1 and R2. Note that although each of the shape defining plates 102 b, 102 c and 102 d also includes its driving mechanism as in the case of the shape defining plate 102 a, the illustration of them is omitted in FIGS. 8 and 9.

As shown in FIGS. 8 and 9, the shape defining plate 102 a is placed and fixed on the slide table T1, which can be slid in the y-axis direction. The slide table T1 is slidably placed on a pair of linear guides Gil and G12 extending in parallel with the y-axis direction. Further, the slide table T1 is connected to the rod R1 extending from the actuator A1 in the y-axis direction. With the above-described configuration, the shape defining plate 102 a can be slid in the y-axis direction.

Further, as shown in FIGS. 8 and 9, the linear guides G11 and G12 and the actuator A1 are placed and fixed on the slide table T2, which can be slid in the z-axis direction. The slide table T2 is slidably placed on a pair of linear guides G21 and G22 extending in parallel with the z-axis direction. Further, the slide table T2 is connected to the rod R2 extending from the actuator A2 in the z-axis direction. The linear guides G21 and G22 and the actuator A2 are fixed on a horizontal floor surface or a horizontal pedestal (not shown). With the above-described configuration, the shape defining plate 102 a can be slid in the z-axis direction. Note that examples of the actuators A1 and A2 include a hydraulic cylinder, an air cylinder, and a motor.

Second Exemplary Embodiment

Next, a free casting apparatus according to a second exemplary embodiment is explained with reference to FIG. 10. FIG. 10 is an enlarged cross section schematically showing a shape defining member 202 of a free casting apparatus according to the second exemplary embodiment. The free casting apparatus according to the second exemplary embodiment is equipped with a heating unit (heater) 20 disposed inside the shape defining member 202. The rest of the configuration is similar to that of the free casting apparatus according to the first exemplary embodiment. Note that the xyz-coordinate system shown in FIG. 10 also corresponds to that shown in FIG. 1.

The heating unit 20 is disposed inside the shape defining member 202 so as to surround the molten-metal passage section 103. As a result, the heating unit 20 can effectively heat the periphery of the molten-metal passage section 103, which comes into contact with the held molten metal M2. Therefore, the free casting apparatus according to the second exemplary embodiment can increase the temperature of the shape defining member 202 to the reference temperature in a shorter time than that of the free casting apparatus according to the first exemplary embodiment. That is, the productivity of the free casting apparatus according to the second exemplary embodiment is better than that of the free casting apparatus according to the first exemplary embodiment. Note that the heating unit 20 may be disposed on the top surface of the shape defining member 202 instead of being disposed inside the shape defining member 202.

Next, a casting control system provided in a free casting apparatus according to the second exemplary embodiment is explained with reference to FIG. 11. FIG. 11 is a block diagram of a casting control system provided in a free casting apparatus according to the second exemplary embodiment. As shown in FIG. 11, this casting control system includes a shape defining member 202, a pulling-up machine 108, a temperature sensor 110, and a casting control unit 111. Note that the shape defining member 202 includes a heating unit 20. Details of the shape defining member 202 are the same as those explained above with reference to FIG. 10. Further, the pulling-up machine 108 and the temperature sensor 110 are similar to those of the first exemplary embodiment, and therefore their detailed explanations are omitted.

The casting control unit 111 starts heating the shape defining member 202 by the heating unit 20 before starting the pulling-up of the starter ST from the molten metal M1. Then, when the temperature of the shape defining member 202 measured by the temperature sensor 110 is lower than the reference temperature, the casting control unit 111 does not start the pulling-up of the starter ST by the pulling-up machine 108 and continues the heating of the shape defining member 202 by the heating unit 20. On the other hand, when the temperature of the shape defining member 202 measured by the temperature sensor 110 reaches the reference temperature, the casting control unit 111 starts the pulling-up of the starter ST by the pulling-up machine 108. At this point, the casting control unit 111 stops the heating of the shape defining member 202 by the heating unit 20. Note that the heating of the shape defining member 202 by the heating unit 20 may be continued when the pulling-up of the starter ST is started. However, by stopping the heating, the power consumption can be reduced.

Note that the present invention is not limited to the above-described exemplary embodiments, and various modifications can be made without departing from the spirit and scope of the present invention.

This application is based upon and claims the benefit of priority from Japanese patent application No. 2013-244004, filed on Nov. 26, 2013, the disclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

-   20 HEATING UNIT -   101 MOLTEN METAL HOLDING FURNACE -   102, 202 SHAPE DEFINING MEMBER -   102 a-102 d SHAPE DEFINING PLATE -   103 MOLTEN-METAL PASSAGE SECTION -   104 SUPPORT ROD -   105 ACTUATOR -   106 COOLING GAS NOZZLE -   107 COOLING GAS SUPPLY UNIT -   108 PULLING-UP MACHINE -   110 TEMPERATURE SENSOR -   111 CASTING CONTROL UNIT -   A1, A2 ACTUATOR -   G11, G12, G21, G22 LINEAR GUIDE -   M1 MOLTEN METAL -   M2 HELD MOLTEN METAL -   M21 SOLIDIFIED PIECE -   M3 CAST METAL -   R1, R2 ROD -   S1 LASER DISPLACEMENT GAUGE -   S2 LASER REFLECTOR PLATE -   SIF SOLIDIFICATION INTERFACE -   ST STARTER -   T1, T2 SLIDE TABLE 

1-11. (canceled)
 12. A pulling-up-type continuous casting method comprising: disposing a shape defining member above a molten-metal surface of molten metal held in a holding furnace, the shape defining member being configured to define a cross-sectional shape of a cast-metal article to be cast; submerging a starter into the molten metal while making the starter pass through the shape defining member; and pulling up the molten metal by pulling up the starter while making the molten metal pass through the shape defining member after a temperature of the shape defining member reaches a predetermined reference temperature, wherein the reference temperature is equal to or higher than a solidification completion temperature of the molten metal and wherein the temperature of the shape defining member is measured by a contact-type temperature sensor fixed on a top-side main surface of the shape defining member.
 13. The pulling-up-type continuous casting method according to claim 12, wherein the reference temperature is equal to or higher than a solidification start temperature of the molten metal.
 14. The pulling-up-type continuous casting method according to claim 12, wherein in the step of disposing the shape defining member, a bottom-side main surface of the shape defining member is brought into contact with the molten-metal surface.
 15. The pulling-up-type continuous casting method according to claim 12, wherein the shape defining member comprises a heating unit that heats the shape defining member itself, and in the pulling-up the molten metal, the shape defining member is heated by the heating unit until the temperature of the shape defining member reaches the reference temperature.
 16. A pulling-up-type continuous casting apparatus comprising: a holding furnace that holds molten metal; a shape defining member disposed above a molten-metal surface of the molten metal, the shape defining member being configured to define a cross-sectional shape of a cast-metal article to be cast; a temperature sensor that measures a temperature of the shape defining member; a pulling-up machine that pulls up the molten metal by pulling up a starter while making the molten metal pass through the shape defining member; and a casting control unit that starts the pulling-up by the pulling-up machine after the temperature of the shape defining member measured by the temperature sensor reaches a predetermined reference temperature, wherein the reference temperature is equal to or higher than a solidification completion temperature of the molten metal and wherein the temperature sensor is a contact-type temperature sensor fixed on a top-side main surface of the shape defining member.
 17. The pulling-up-type continuous casting apparatus according to claim 16, wherein the reference temperature is equal to or higher than a solidification start temperature of the molten metal.
 18. The pulling-up-type continuous casting apparatus according to claim 16, wherein the shape defining member is disposed so that its bottom-side main surface is in contact with the molten-metal surface.
 19. The pulling-up-type continuous casting apparatus according to claim 16, wherein the shape defining member comprises a heating unit that heats the shape defining member itself.
 20. The pulling-up-type continuous casting apparatus according to claim 19, wherein the heating unit is disposed on a periphery of a molten-metal passage section through which the molten metal passes in the shape defining member.
 21. The pulling-up-type continuous casting apparatus according to claim 19, wherein the casting control unit instructs the heating unit to heat the shape defining member until the temperature of the shape defining member measured by the temperature sensor reaches the reference temperature. 